Apparatus for utilizing detonation waves



Jan. 20, 1959 w. c. M GILL 2,869,924

APPARATUS FOR UTILIZING DETONATION WAVES Filed March 28, 1955 Purging Gas m m! i 26 L Oxidanf INVENTOR 3 WILLIAM c. McGlLL 1'2 BY Powder ATTORNEY UTILIZING DETONATIO WAVES William C. McGill, Speedway, Ind., assignor to Union Carbide Corporation, a corporation'of New York Application March 28, 1955, Serial No. 497,036

6 Claims. (Cl. 299-286) APPARATUS FOR The present invention relates to improved apparatus for utilizing detonation waves for coating and other purposes.

In patent application Serial No. 275,332, filed on March 7, 1952, by -R. M. Poorman, et al., issued on August 2, 1955, as Patent No. 2,714,563, apparatus is disclosed in which detonation waves are utilized'to transmit energy to powder particles which are suspended in a detonated fluid charge. Utilizing this energy, the powder particles are heated to a high temperature and accelerated to a high velocity, whereby they may be utilized to form coatings on surfaces of bodies.

In the method of operation of this apparatus, a charge of a detonatable fluid mixture is first formed by feeding a fuel gas and oxidant through valve means into a chamber where mixing takes place. The asformed detonatable mixture is then passed to an elongated barrel and powder particles are suspended inthe mixture as it enters the barrel. Upon admission of a 1 proper charge, the fuel and oxidant valves close and pressure Within the apparatus, are forced out the openend of the barrel. The next cycle is then begun by closing the purging gas valve and reopening the fuel and oxidant valves for the entry of fuel and oxidant to the mixing chamber for the formation of the next detonatable fluid mixture. Many of these cycles may be carried out per second.

It has been'found that the apparatus of the Poorman at al. patent presents certain difficulties which alfect the continued operation of the apparatus over long periods of time. The prime difficulty is that the purging gas valve of this apparatus is open during that part of the cycle when the detonation occurs; Under these conditions the back surge 'of-hot gases following the detonation flows through the openlpurging gas valve and decomposes the oil in the valve guide of the purg ing gas valve and on the heads of the fuel and oxidant valves. The resulting carbon formation combines with a similar formation resulting from the combustion process to form a sticky, gummy deposit on and around the open purging gas valve as well as the surfaces of the closed fuel and oxidant valves. With continued operation this deposit build-up is such that the valves stick and erratic operation occurs.

Accordingly, it is the main object of the present invention to provide improved apparatus for utilized detonation waves, wherein valves for the control of fuel, oxidant and purging gases are arranged so as to eliminate the deposition problem described above.

Other aims and advantages of the invention will be apparent from the following description and appended In the drawing, Fig. l is a schematic view of improved apparatus for utilizing detonation waves arranged so as to protect the'purging gas valve; and Fig. 2 is a partial schematic View of apparatus for utilizing detonation waves modified to'offer further protection to the fuel and oxidant valves as well as the purging'gas valve;

Referring specifically to the embodiment of Fig. 1 of the drawing, a detonation gun D is provided having an elongated barrel 10, powder entry tube means '12 for supplying powder to said barrel, ignition means 14,

end of barrel 10.

Mixing block 18 contains a mixing chamber 20 wherein a fuel gas and' an oxidizing gas are "mixed to form a detonatable'gasrnixture' before passage to thebarrel lll'of the gun. '1

Fuel' gas, such as acetylene, passes from a suitable including a spark plug 16; and mixing block 18'at one source (not shown) through fuel conduit means ZZ'and means 30 and purging gas valve'means' 32 of mixing fblockdS topurging gas chamber 34 and gas flowresist- 3 ance conduit 36 which communicates with mixing cham be'riliin such a manneras topass the'purging gas over both the oxidant gas valve 28 and the'fuel gas valve. 24'; The path'followed by the purging gas in its in thezdrawing;

passage through mixiug'block' 18. is indicated by arrows As described at great length in Patent No. 2,714,563, thc'operating'cycle-for the detonation gun is as follows:

An electric niotor40 isbelted totshaft 42' which drives threecams 441, 46 and'48. Cam 44 regulates the opening and closing of fuel andoxidant'valves 24 'a'nd28, respec tively; in the mixer block '18. Upon the" opening of these valves charges of these gases pass to mixing cham ber 29 and into the barrelltl of the gun. A'duantity of powder is'suspendedin"the detonatable mixture 'as it passes powder entry'tube means 12 in the barrel 1-0.' When a sufficient charge of "detonatable mixture has been ad: mitted'to the barrel'iti, 'cam" 44 closes valvesf24 'and 23, whileicamfio rotates to the'position"(shown in "the" draw ing at which the pur ing gas stream flows through the mixingblock 18, 'pastvalves 2"4fand 28 and'to the'barrel Iii." this pointin time, closes the ignitioh '5 circuit through switch 50, thereby energizing the; circuit ont a ba ery 52 a d sha k i 5.4- Th s a k l ver 'a" a k vo ta e ta ting a d. he de 'h m nut i h ane t sn and. e ema and associated phenomenaoccur devlopthe which propels the suspended powder and combustion products at high velocity and temperature from the open end 56 of barrel 10.

It has been found that the provision of the conduit 36 between mixing chamber 20 and chamber 34, with its added length of gas-filled tube, produces a cushioning effect on the back surge of combustion gases from the barrel during the formation of the detonation phenomenon. This cushioning efiect prevents the back surge of these 'hot combustion products to the open purging gas valve 32, thereby preventing the formation of carbon deposits on the purging gas valve which, if they occurred,

Patented Jan. 20, 1 959 nergy would prevent the proper opening and closing of the valve.

The length required for the conduit 36 is only that sufiicient to prevent the back-surging combustion products from reaching the purging gas valve, and is dependent upon the temperature and pressure of the gases in the barrel of the gun as well as the length of time during which these hot gases can surge backwards towards the gas valves. The former is dependent on the composition of the combustible mixture, while the latter is dependent on the length and diameter of the gun barrel. It has been found however that the provision of a 21 inch, inch diameter path (including the gas flow resistance conduit) between the point of ignition and the valve to be protected in which path the gases are required to change their direction of flow 90 at least ten times, is the minimum requirement for the elimination of back surge which will produce harmful carbon depositions on the valve. Only some of the changes in flow direction are shown in the schematic views of the draw ing, but an arrangement of such changes is readily determinable by one skilled in the art and having this disclosure. The cross-sectional area of the conduit is determined by the flow requirements of the purging gas stream and need not be changed to accomplish the desired cushioning effect on the back-surging combustion gases.

A detonation gun embodying the invention and similar to that shown in Fig. 1 of the drawing having a 1.0" I. D. barrel and a mixing chamber having a 0.1406 square inch cross-sectional area was operated employing acetylene as the fuel gas and oxygen as the oxidant with a 1:1 fuel-to-oxidant ratio. Nitrogen was employed as the purging gas and a gas flow resistance conduit having a I. D. and a 12" length was used. This gun was operated for 20 hours without any harmful carbon deposition on the purging gas valve.

The embodiment shown in Fig. 2 of the drawing is similar to that of Fig. 1 except that protection is additionally provided for the fuel and oxidant valves by positioning the conduit 36 between mixing chamber 20 and barrel rather than between the purging gas inlet chamber 34 and mixing chamber 20. Apparatus of this type was operated under conditions otherwise identical to those set forth in the example above and no harmful carbon deposition was found on any of the gas valves.

What is claimed is:

1. In a detonation gun having an elongated barrel, provided with an open end, of length and diameter to permit the formation in a fluid fuel charge of a detonation, a mixing chamber communicating with said barrel having therein fuel and oxidant gas valves and conduit means including a purging gas valve for controlling the supply of a purging gas positioned and arranged to pass a purging gas over said fuel and oxidant valves when said valves are closed; the improvement which comprises providing, between said barrel and at least one of said valve means to be protected, a gas flow resistance conduit of sufiicient length to prevent the back surge of combustion gases from said detonation from passing back to said valve means.

2. In a detonation gun having an elongated barrel, provided with an open end, of length and diameter to permit the formation in a fluid fuel charge of a detonation, a mixing chamber communicating with said barrel having therein fuel and oxidant gas valves and conduit means including a purging gas valve for controlling the supply of a purging gas positioned and arranged to pass a purging gas over said fuel and oxidant valves when said valves are closed; the improvement which comprises providing a path at least 21 inches in length and inch in diame er having at least ten changes in direction of degrees between said barrel and at least one of said valves to be protected from the back surge of combustion gases thereto.

3. In a detonation gun having an elongated barrel, provided with an open end, of length and diameter to permit the formation in a fluid fuel charge of a detonation, a mixing chamber communicating with said barrel having therein fuel and oxidant gas valves and conduit means including a purging gas valve for controlling the supply of a purging gas positioned and arranged to pass a purging gas over said fuel and oxidant valves when said valves are closed; the improvement which comprises providing in said purging gas conduit means, between said purging gas valve and said mixing chamber, a gas flow resistance conduit of sufficient length to prevent the back surge of combustion gases from said detonation from passing back to said purging gas valve means.

4. Apparatus in accordance with claim 3, wherein said path between said barrel and said purging gas valve means, including said gas flow resistance conduit, is at least 21 inches in length, /8 inch in diameter and has at least ten changes in direction of 90 degrees.

5. In a detonation gun having an elongated barrel, provided with an open end, of length and diameter to permit the formation in a fluid fuel change of a detonation, a mixing'chamber communicating with said barrel having therein fuel, oxidant and purging gas valve and conduit means for controlling the supply of a purging gas positioned and arranged to pass a purging gas over said fuel and oxidant valves when said valves are closed; the improvement which comprises providing, between said barrel and said mixing chamber, a gas flow resistance conduit of sufi'icient length to prevent the back surge of combustion gases from said detonation from passing back to said mixing chamber.

6. Apparatus in accordance with claim 5, wherein said path between said barrel and said mixing chamber including said gas flow resistance conduit, is at least 21 inches in length, inch in diameter and has at least ten changes in direction of 90 degrees.

References Cited in the file of this patent UNITED STATES PATENTS 804,002 Fouche Nov. 7, 1905 2,397,165 Shepard Mar. 26, 1946 2,427,448 Duccini et al. Sept. 16, 1947 2,544,259 Duccini et al. Mar. 6, 1951 2,626,860 Dorf Jan. 27, 1953 2,714,563 Poorman et al Aug. 2, 1955 

